This application claims the priority of German application 196 54 473.4, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a multistation press for the successive machining of workpieces in several stages, and more particularly, to a press having several press stations which are arranged behind one another and through which the workpiece passes successively, having at least one transfer device for transporting the workpiece, having a common driving device for all press stations which has a drive shaft divided into shaft sections, at least one press station being assigned to each shaft section to, and having slides which are driven by the drive shaft and which are assigned to one press station respectively.
EP 0 439 684 B1 discloses a stamping press which has a frame, a drive, a slide device driven by the drive, and a base plate device. A drive shaft is divided into shaft sections assigned to the slide sections. The slide sections are independent of one another. The base plate device is divided in the same manner into base plate sections which are supported independently of one another. As the result, the lower dead center positions of the individual slides are to be fixed in a phase-shifted manner in order to reduce the overall stress to the machine. As a result, to use long and narrow tools must be used.
It is a disadvantage that the known phase shifting referred to above is fixedly adjusted, whereby the press can be optimally designed only for one operating point. In this case, the phase shifting between the slide sections must naturally always be adjusted to the worst case with respect to the drawing depth, the workpiece width, etc.
DE-PS 1 452 772 describes a transfer press having a main slide and one or several additional slides. The additional slides with respect to the main slide pass through the lower dead center-point in a time-shifted manner to avoid press load peaks. It is also a disadvantage that the individual slides are in a fixed phase shift with respect to one another. As a result, the number of strokes of the press cannot be raised above a specific upper level.
It is therefore an object of the present invention to provide a multistation press in which the conditions with respect to the passage time and the stroke number are optimal for each specific workpiece, so as to achieve an increased yield. In particular, an adaptation of the phase shift of the individual press stations optimally to the stroke number of the press is now possible.
According to the present invention, this object has been achieved by the multistation press by providing that one or more adjusting devices change one or more phase shifts.
The adjustable coupling according to the present invention allows the individual press stations to be adjusted very precisely to their specific characteristics, such as the shape and the size of the workpiece and thus of the tool, the forming degree, the drawing depth and additional influencing variables occurring during the forming of sheet metal, whereby the entire pressing operation can be variably configured. The phase shift can advantageously be adjusted in a targeted manner to each individual drawing depth or other specific conditions of a press station.
On one hand, it is now possible to provide more time for the transport of the workpieces, and particularly determine the precise time duration for the transport because the slide of the individual press station can be adjusted to reach the lower dead center at an arbitrarily adjustable later point in time.
On the other hand, the slides can now also be moved at a higher rate because the loss of time resulting from this higher speed for the transport system can be compensated. That is, the slide of the following press station passes at a later point in time through the lower dead center and the transport system therefore has the same time available as previously.
Furthermore, the present invention makes possible the compensation of a longer transport path to be covered, which may occur for various reasons, by way of a variable adjusting of the coupling, and thus of the movement, of the respective slide.
Because multistation presses usually have a very long service life, new workpieces, new tools or new technologies may result in changes with respect to the use of the press. These changes can normally not be taken into account during the construction of the machine. The adjustable coupling of the present invention now makes it possible to better adapt multistation presses to different tools or workpieces, and also to make changes later or to take customers"" wishes into account.
As the result of the multistation press constructed in accordance with the present invention, the stroke number can be adapted to the press conditions and in many cases can be increased. This also results in the rise of the ejected parts by the machine, because this yield depends directly on the number of press strokes. The adjustment of the couplings can be carried out as a function of different parameters within the multistation press, such as the workpiece transport path, the tool size or the workpiece drawing depth.
An optimal adaptation of the multistation press and of the pressing operation taking place in the multistation press to the above-described parameters which are decisive for the pressing operation now result. Different devices may be provided for adjusting the couplings. Particularly simple adjusting possibilities are achieved with a locking device of the drive shaft, a locking device of one of the slides or of a pressure point adjusting device. It is only necessary to be able to lock the drive at any point in order to be able to adjust the individual couplings to the respective conditions.